IAC valve not working?

[rumblecloud]

How do you know?
This started with a CEL and codes 172, 176 and 177. I've worked thru that with RonD and those codes are taken care of to the point that I am no longer receiving those codes.
I still have the same issue. Starts and runs ok when cold. As it warms the idle get erratic and eventually stalls. So I'm chasing vacuum leaks. I've warmed the truck. unplugged the IAC and there is no change in the rpm. Left it unplugged (per RonD in another post) and started unplugging the different vacuum hoses. eadh one resulted in a drop in rpm and an occasional stall.

I've started iti cold and driven for maybe a mile with no real issues. It seems as soon as the engine hits normal operating temp, it starts to lose power and when I hit the accelerator, it bogs down and eventually stalls. Wait about five minutes and all is normal for about five minutes and the cycle repeats.,

Sorry if I am posting this as a new issue. It may be realted to the CEL thingy.

Thanks for any iinput.

 

[franklin2]

When you unplug the idle air control valve, the rpms should drop very low. Since the don't, either you have air coming in feeding the engine from somewhere else, or someone has messed with the idle stop screw and that needs to be turned back. That would be something you could experiment with. Mark the idle stop screw so you can put it back where it was, and then with the engine running, the IAC unplugged, turn the idle stop screw back. You should be able to make the engine stall by turning the screw back. If it keeps running, you have a lot of air coming in from somewhere else that the engine is using to run on.